Bonded and nonbonded charge concentrations and their relation to molecular geometry and reactivity

Bader, R. F. W.; MacDougall, Preston J.; Lau, C. D. H.

doi:10.1021/ja00318a009

Cited by 581 publications

(395 citation statements)

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“…This L(r) feature is in conformity with a partially vacant Ni(dz 2 ) orbital since the Laplacian is a well-established and experimentally accessible indicator to map regions of local charge concentration (L(r) > 0 eÅ -5 ). [16] The bond path between the -agostic hydrogen atoms and the metal center in 2 thus represents an attractive donor interaction in the charge density picture (Figure 3). We note, that an endocyclically curved M•••H-C bond path topology has been also experimentally observed in case of -agostic d 0 transition metal alkyls (e.g.…”

Section: Orbitals In M•••h-c Interactions"mentioning

confidence: 99%

Anagostic Interactions under Pressure: Attractive or Repulsive?

et al. 2015

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Square‐planar d8‐ML4 complexes might display subtle but noticeable local Lewis acidic sites in axial direction in the valence shell of the metal atom. These sites of local charge depletion provide the electronic prerequisites to establish weakly attractive 3c–2e M⋅⋅⋅HC agostic interactions, in contrast to earlier assumptions. Furthermore, we show that the use of the sign of the 1H NMR shifts as major criterion to classify M⋅⋅⋅HC interactions as attractive (agostic) or repulsive (anagostic) can be dubious. We therefore suggest a new characterization method to probe the response of these M⋅⋅⋅HC interactions under pressure by combined high pressure IR and diffraction studies.

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Section: Orbitals In M•••h-c Interactions"mentioning

confidence: 99%

Anagostic Interactions under Pressure: Attractive or Repulsive?

et al. 2015

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“…Popelier proposed that these type of studies form a unified theoretical framework, named Quantum Chemical Topology (QCT) inspired in the seminal work of Bader, [48,49,51,[69][70][71] for general topological analysis of scalar functions, such as the source function, [72] the momentum density, [73] the electron pair density, [74] the nuclear potential energy field, [75] the virial field, [76] as well as the Laplacian of charge density. [48,53,77,78] In fact, topological analysis of various scalar fields, different to electron density, is now used in computational chemistry, such as the scalar field derived from the molecular electrostatic potential [79] ; even the mathematical framework of topological analysis has been applied by Mezey on the study of potential energy hypersurfaces. [80,81] Chemical reactions are always associated with electronic density changes of the involved chemical species.…”

Section: Electron Density Q(r)mentioning

confidence: 99%

Unraveling reaction mechanisms by means of Quantum Chemical Topology Analysis

Andrés

González-Navarrete

Safont

2014

Int J of Quantum Chemistry

100

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A chemical reaction can be understood in terms of geometrical changes of the molecular structures and reordering of the electronic densities involved in the process; therefore, identifying structural and electronic density changes taking place along the reaction coordinate renders valuable information on reaction mechanism. Understanding the atomic rearrangements that occur during chemical reactions is of great importance, and this perspective aims to highlight the major developments in quantum chemical topology analysis, based on the combination of electron localization function and catastrophe theory as useful tools in elucidating the bonding and reactivity patterns of molecules. It reveals all the expected, but still ambiguous, elements of electronic structure extensively used by chemists. The chemical bonds determine chemical reactivity, and this technique offers the possibility of their visualization, allowing chemists to understand how atoms bond, how and where bonds are broken/ formed along a given reaction pathway at a most fundamental level, and so, better following and understanding the changes in the bond pattern. Their results clearly herald a new era, in which the atomic imaging of chemical bonds will constitute a new method for examining chemical structures and reaction mechanisms. The important feature of this procedure is that in practice the scope of its values is systemindependent. In addition, from a practical point of view, it is cheap to calculate and implement because wave functions are the required input, which are easily available from standard calculations. To capture these results two reaction mechanisms: isomerization of C(BH) 2 carbene and the thermal cycloheptatriene-norcaradiene isomerizations have been selected, indicating both the generality and utility of this type of analysis.

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“…It is well documented (6,13,14) that centres of charge concentration in the VSCC serve as sites of electrophilic attack, while the centres of charge depletion play the corresponding role in nucleophilic attack. The localized charge concentrations in the VSCC of carbon in a saturated hydrocarbon are, of course, all bonded concentrations and as such are relatively u~eactive towards electrophiles.…”

Section: A -mentioning

confidence: 99%

“…The Laplacian of the charge density, the quantity V2p, determines the points within a molecule where electronic charge is locally concentrated and depleted (5,6). The susceptibility of the carbocations to the addition of a nucleophile is related to the properties of their Laplacian distributions, and the relative inertness of the hydrocarbons to either nucleophilic or electrophilic attack is accounted for in the same manner.…”

Section: Introductionmentioning

confidence: 99%

Properties of atoms and bonds in carbocations

Bader¹

1986

Can. J. Chem.

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The quantum theory of atoms in molecules defines structures for and determines the properties of the atoms and bonds in the series of carbocations [(CH3),CH3_,]+ with n = 0-3, and their parent hydrocarbons. In this theory, an atom in a molecule and its properties are defined by quantum mechanics. The quantum condition defining the atom is given in terms of a property derived from the charge density, as are the other concepts of the molecular structure hypothesis. In terms of the amount of electronic charge density accumulated between the carbon nuclei and its spatial distribution, a C-C bond of the carbocations exhibits an order greater than one. There is a transfer of charge from the hydrogens of methyl to the central carbon that destroys the axial symmetry of these C-C bonds and concentrates the charge in a plane perpendicular to the plane of substitution, in a manner consistent with the hyperconjugative mechanism of electron transfer. The positive charge of a carbocation is thus delocalized over all the atoms in the molecule, and the extent of this delocalization increases with increased methyl substitution. The electron population of each atom in a carbocation increases with this increase in the delocalization of positive charge and its energy is correspondingly decreased (the atom becomes more stable). These effects are most pronounced for the carbon atom bearing the methyl groups and they account for the observed increase in the relative stabilities of the carbocations with increasing methyl substitution. The electron populations and energies of the atoms in saturated hydrocarbons are also determined. The group additivity scheme for the energy in the homologous series of normal alkanes is predicted and explained in terms of the properties of the quantum atoms. It is the possibility of such transferability of the quantum atoms and their properties between systems that identifies them with the atoms of chemistry.R. F. W. BADER. Can. J. Chem. 64, 1036 (1986).La thCorie quantique des atomes dans les molCcules dCfinit les structures et dCtermine les properiCtCs des atomes et des liaisons dans une sCrie de carbocations [(CH~),CH~-~]+, dans lesquels n = 0-3, ainsi que dans leurs hydrocarbures de base. Dans cette thCorie, la condition quantique qui dCfinit l'atome ainsi que les autres concepts de l'hypothbse relative i la structure molCculaire sont dCfinies en fonction d'une propriCtC dCrivCe de la densit6 de charge. En termes de la densit6 de la charge Clectronique qui est accumulCe entre les noyaux de carbone et de leur distribution spatiale, une liaison C-C des carbocations prksente un ordre qui est plus grand que un. I1 se produit un transfert de charge des hydrogbnes du mCthyle vers le carbone central et ceci dCtruit la symktrie axiale de ces liaisons C-C et concentre la charge dans un plan perpendiculaire au plan de la substitution, d'une manikre qui est en accord avec le mecanisme d'hyperconjugaison de transfert Clectronique. La charge positive d'un carbocation est donc dClocalisCe sur tous les atomes de la...

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Bonded and nonbonded charge concentrations and their relation to molecular geometry and reactivity

Cited by 581 publications

References 1 publication

Anagostic Interactions under Pressure: Attractive or Repulsive?

Anagostic Interactions under Pressure: Attractive or Repulsive?

Unraveling reaction mechanisms by means of Quantum Chemical Topology Analysis

Properties of atoms and bonds in carbocations

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